In my humble opinion, I put Jackie Robinson as the most influential athlete in American sports history and maybe in World history. The impact on future black athletes is incalculable, his breaking the color line brought a minority in a lot of homes that otherwise that might have not happened.
Branch Rickey, The President of the Dodgers at the time, had to wait for the Commissioner Mountain Landis (he was a stout racist) to pass away before trying his luck bringing in a black Baseball player. It makes sense it would have been Branch Rickey to try this first as he started the farm system that went league wide while he was with the St. Louis Cardinals. I imagine Branch Rickey looking at the Negro Leagues and cursing as this bunch of great players were out of his reach.
In 1947, Jackie Robinson broke the color-line in MLB, becoming one of the 1st black people in American History to have the same rules and full equality, and no one to take it away. It didn't start easy, Jackie went through brutal slurs, hostile teammates/opponents, and race crazed fans. His wife Rachel was always in the stand terrified for herself and husband safety. He kept his cool as Mr. Rickey had told him the importance of turning the other cheek and let his play on the field speak for itself. It worked, Jackie won the Rookie of the year in 1947 then the MVP in 1949 at age 30. after this, Jackie gave it back to the fans and others after establishing himself as a Superstar.
Hank Aaron, Frank Robinson, Willie Mays, Bob Gibson and every others wouldn't be around had it not been for Jackie's patience for being accepted by the American Public. Jackie was one of the reason the civil rights movement gained momentum and attention by White America. Having Black Athletes being the Hero and making fans proud paved the way for many children and adults having a different perspective on race, though it was still far from where it needs to be.
Jackie Robinson day is one of my favorite sports days, as without the man the landscape of this country would be much different.
Thank you, Jackie